Model studies directed towards microalgal polyether toxins. Use of 2-phenyl-sulphonyl cyclic ethers in the preparation of trans, syn, trans α-alkyl, β-hydroxy-substituted tetrahydropyran subunits

A synthesis of opticaLLy active C-7- and C-8 -tetrahydropyranyl subunits with suitable functionalities for further elaboration of transfused polyether toxins was achieved from glucal acetate via the use of 2-phenylsulphonyl intermediates. The bicyclic trans,syn,trans oxane-oxepanyl substructure 26 was prepared through the application of this methodology.